This invention relates to sliding bearings for use in precision slides such as are employed, for example, in precision machine tools such as engine lathes.
In a precision slide in which a slide member is constrained by one or more longitudinal guide shafts to be moved along a rectilinear path the slide member is commonly mounted on bearings which engage the shafts to facilitate the smooth rectilinear movement of the slide. Typically, each bearing assembly comprises a bearing block having an internal passageway through which the shaft extends and housing one or more bearing sleeves lined with antifriction material, the bearing sleeve or sleeves being a press fit in the housing. It is necessary to keep the clearance between the relatively sliding surfaces of the sleeve or sleeves and the shaft to a minimum, in order to ensure accurate rectilinear movement of the slide, but with the current practice it is impossible to reduce the clearance to zero and so there is a limit to the accuracy which can be achieved. Alternatively, ball bearing assemblies have been employed for the purpose, but apart from the matter of cost, such assemblies have the disadvantage of low load capacity and high starting friction due to dust seals which make it difficult to control the movement of the slide accurately.